1. Field
Aspects of the present invention relate to a battery pack.
2. Description of the Related Art
In general, unlike a primary battery which is not designed to be recharged, a secondary battery is capable of being repeatedly charged and discharged. A low-capacity secondary battery composed of a single battery cell is used as a power source for various small, portable electronic devices, such as cellular phones, notebook computers, cameras, and camcorders. A high-capacity secondary battery in which a plurality of battery cells are coupled to (e.g., connected to) each other in a pack structure is used as a power source for driving a motor of a hybrid electric vehicle (HEV), an electric vehicle (EV), and the like.
Several to several tens of secondary battery cells may be mounted in a battery unit and coupled to each other to form a battery pack. A plurality of battery cells may be coupled to (e.g., connected to) one another via a busbar to form the battery pack. In the secondary battery cells, aluminum or an aluminum alloy may be used as a positive electrode terminal and copper or a copper alloy may be used as a negative electrode terminal. The busbar is welded to respective negative electrode terminals and positive electrode terminals of adjacent ones of the plurality of secondary batteries to couple the plurality of secondary batteries to each other in series to form a large-capacity battery pack. However, when the busbar is made of a metal, such as copper or aluminum, it is difficult to weld different kinds of metals to each other. To overcome the problem, the busbar may be formed of clad metal including copper and/or aluminum. In this case, however, because the clad metal busbar is expensive, the manufacturing cost may increase. However, copper-copper laser welding is complicated, making it difficult to achieve the laser welding.